Author Topic: 428 piston pics  (Read 1467 times)

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plovett

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428 piston pics
« on: October 23, 2020, 11:11:40 PM »
What does this look like?

pl

blykins

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Re: 428 piston pics
« Reply #1 on: October 24, 2020, 05:37:09 AM »
To me, it looks like someone didn't deburr the bottoms of the cylinders.  Could also be insufficient clearance. 
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My427stang

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Re: 428 piston pics
« Reply #2 on: October 24, 2020, 07:54:21 AM »
Agree completely, are you trying to reuse?
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Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
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fastf67

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Re: 428 piston pics
« Reply #3 on: October 24, 2020, 09:21:31 AM »
That is a clearance issue. To high up on the skirt. Mike

wowens

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Re: 428 piston pics
« Reply #4 on: October 24, 2020, 09:46:58 AM »
Ring lands look like very short run time. Skirts dry on install, not enough clearance,  or dirty piston at install.
Do they all look like that?

plovett

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Re: 428 piston pics
« Reply #5 on: October 24, 2020, 10:04:28 AM »
Ring lands look like very short run time. Skirts dry on install, not enough clearance,  or dirty piston at install.
Do they all look like that?

I'll find out later today if they all look like that.  Not very short run time.  Several thousand miles, somewhere between 5 and 10K.  The rest I am not sure about.

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plovett

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Re: 428 piston pics
« Reply #6 on: October 24, 2020, 01:43:45 PM »
Yup, they all look like that.  Not all to the same degree, but yes.  You can see the corresponding wear on the cylinder walls.

pl

blykins

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Re: 428 piston pics
« Reply #7 on: October 24, 2020, 02:38:05 PM »
Take a pic of the bottom of the cylinder.

If there’s a sharp edge there, it will roll the aluminum off the piston and then you get metal up in the cylinders.
Brent Lykins
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plovett

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Re: 428 piston pics
« Reply #8 on: October 24, 2020, 04:36:28 PM »
Take a pic of the bottom of the cylinder.

If there’s a sharp edge there, it will roll the aluminum off the piston and then you get metal up in the cylinders.

WILCO on that.  I ran my finger along the bottom of the cylinders and it didn't feel like a sharp edge to me, but I will take a pic.

thanks,

pl

My427stang

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Re: 428 piston pics
« Reply #9 on: October 24, 2020, 05:03:52 PM »
Probably was one when fresh, just burnished itself over time...hard to avoid if you don't knock it down during prep
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Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

plovett

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Re: 428 piston pics
« Reply #10 on: October 24, 2020, 06:14:25 PM »
Hard to get a good pic with the crank in there.  I will take another one after it's out.  The bottom edge of the cylinder feels "half-way sharp edged".  Definitely not a large chamfer or radius there, but not sharp either.

The pattern is only on the thrust sides.

pl

WConley

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Re: 428 piston pics
« Reply #11 on: October 24, 2020, 08:21:11 PM »
Piston skirt scuffing typically happens right away - on first fire-up.  As mentioned above it can be due to dirt, a sharp bottom edge, or tight piston-bore clearance.

At Ford we did a lot of work with skirt coatings to eliminate scuffing with tight pistons.  We were going tight to minimize NVH for future engines.  Even though the coating would wear away quickly, it did its job in those critical first few seconds...
A careful study of failure will yield the ingredients for success.

fastf67

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Re: 428 piston pics
« Reply #12 on: October 24, 2020, 10:10:47 PM »
Yes material will score up high on piston and cylinder from debris (should have explained better) but at the point of bottom dead center the amount of piston skirt out of a sharp edge cylinder will show a more pronounced area or scored harder usually at that point. Widest point of piston is around 3/4 of the way down but need to check you spec sheet as everyone is a little different. Pistons are not round nor are they tapered evenly, more like a offset whiskey barrel shape taper. The pistons in the pics are very evenly scored is leading me to believe it is a clearance or lube problem. This is just a guess from a pic though. Any crank scraper or screen stopping the lubrication on the walls? Most all rods are direction sensitive and yours are to as they have a oil passage to hit the thrust wall, any problems there? Just throwing it out there.
http://blog.diamondracing.net/how-to-check-piston-to-wall-clearance.

plovett

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Re: 428 piston pics
« Reply #13 on: October 25, 2020, 01:12:32 PM »
I'd say Brent-o-bean is correct.  This is the worst cylinder, number 5.  It looks like a sharp edge and "scrape-age" occurred there.  It might not be the only issue, but it looks like one.

pl
« Last Edit: October 25, 2020, 01:36:41 PM by plovett »

plovett

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Re: 428 piston pics
« Reply #14 on: October 25, 2020, 01:17:17 PM »
Agree completely, are you trying to reuse?

Not reusing.  Just intellectual curiosity...and mechanical prophylaxis.  Not reusing pistons.

pl

« Last Edit: October 25, 2020, 01:58:34 PM by plovett »